1. Field of the Invention
The present invention relates to a kokumi-imparting agent and composition, which includes a peptide showing a CaSR agonist activity. Moreover, the present invention also relates to a food, beverage, and/or seasoning composition which includes a peptide showing a CaSR agonist activity in a concentration of not less than a predetermined level.
2. Description of the Related Art
Consumers' demands on the taste and palatability of foods have recently increased due to, for instance, the diversity of human eating habits. The taste and palatability of a food have conventionally been expressed by the five basic tastes: sweet, salty, sour, bitter and umami. However, at the same time, the development of an agent or composition capable of imparting “kokumi” to a food has been desired. Kokumi means a taste that cannot be expressed by the five basic tastes, and also includes marginal tastes of the basic tastes, such as thickness, growth (or mouthfullness), continuity, and harmony.
The calcium sensing receptor (CaSR) can also be referred to as the calcium receptor, and the signals from the receptor control a variety of biological functions within living bodies. Substances with CaSR agonist activity can be used as a kokumi-imparting agent (see International Patent Laid-Open No. 2007/055393, Pamphlet; International Patent Laid-Open No. 2008/139945, Pamphlet; and The Journal of Biological Chemistry, (2010), 285 (2), 1016-22).
There are a variety of taste-developing patterns for describing “kokumi”. In this respect, there has been an intensive need, in particular, for the development of a kokumi-imparting agent capable of imparting the kokumi to a food, and such agent have a taste-developing pattern of kokumi whose profile is an initial taste type. Moreover, the agent or composition for imparting kokumi can, in general, be used in, for instance, foods and accordingly, it should be highly stable. In addition, the agent or composition for imparting the kokumi should be able easily produced at a low cost from the industrial standpoint.
Accordingly, much research has been conducted on a variety of compounds possessing the desired CaSR agonist activity with the goal of isolating a substance or agent capable of imparting kokumi to other substances, such as foods and beverages, in a superior manner. In particular, the substance or agent should possess a kokumi-imparting effect whose profile is the initial taste-imparting type, be highly stable, and be easily produced at a low cost. Such a kokumi-imparting agent or substance can be used alone, or as an ingredient in a more complex composition which can include the substance and other substances possessing the CaSR agonist activities in combination.
γ-Glutamyl peptides having a γ-glutamine residue at the N-terminal thereof have been reported as being used as synthesized substrates in, for instance, research of enzymatic activities (International Patent Laid-Open No. 2007/066430, Pamphlet; Molecular Pharmacology (1982), 21(3), 629-36; Agricultural and Biological Chemistry (1981), 45(12), 2839-45; and Journal of Biological Chemistry (1979), 254(12), 5184-90). However, there have been no reports to date of the use of γ-Glu-Nva in food, or that it even exists in nature.